Heart valve prosthesis

The functioning of natural heart valves is characterised by many advantages:

• Minimal regurgitation - This means that the amount of blood lost upstream as the valve closes is small. For example, closure regurgitation through the mitral valve would result in some blood loss from the left ventricle to the left atrium as the mitral valve closes. Some degree of valvular regurgitation is inevitable and natural (Fixme: Give indicative value). However, several heart valve pathologies (e.g. rheumatic endocarditis) may lead to clinically significant valvular regurgitation. A desirable characteristic of a heart valve prosthesis is that regurgitation is minimal over the full range of physiological heart function (i.e. various combinations of cardiac output vs. heart rate).
• Minimal transvalvular pressure gradient - Whenever a fluid flows through a restriction, such as a valve, a pressure gradient arises over the restriction. This pressure gradient is a result of the increased resistance to flow through the restriction. Natural heart valves have a low transvalvular pressure gradient as they present little obstruction to the flow through themselves (Fixme: Give indicative value). A desirable characteristic of a heart valve prosthesis is that their transvalvular pressure gradient is as small as possible.
• Non-thrombogenic - As natural heart valves are lined with an endothelium continuous with the endothelium lining the heart chambers they are are not normally thrombogenic. This is important as should thrombus form on the heart valve leaflets and be seeded with bacteria, so called "bacterial vegetations" will form. Such vegatations are difficult for the body to remove as the normal physiological defense mechanisms that would remove such vegatations are not present on the valve leaflets i.e. they are avascular with a largely connective tissue composition (Fixme: Create article discussing the pathgonesis of leaflet bacterial vegatations.). Should bacterial vegatations form on the valve leafets they may continually seed bacteria into the arterial tree which may lead to bacteremia or septicaemia. Portions of the vegatation may also break off and form septic emboli. Septic emboli can lodge anywhere in the arterial tree (e.g. brain, bowel arterial cascade, lungs) leading to local infectious foci. Even fragments from non-infective vegetations (Fixme: Is this the correct terminology) can be hazardous as they can lodge and block downstream arteries (e.g. coronary arteries leading to myocardial infarction, cerebral arteries leading to stroke). A desirable characteristic of a heart valve prosthesis is that they are non-thrombogenic or minimally thrombogenic.
• Self-repairing - (STD)

• Biological heart valves
  • Allograft/autograft/isograft
  • Xenograft
• Artificial heart valves
  • Percutaneous implantation
    • Stent framed
    • Not framed
  • Sternotomy/Thoracotomy implantation
    • Tilting disk
    • Bi-leaflet
    • Tri-leaflet

(Editing note: Will be spending an hour or so a day to build up this article.)

• Page describing types of heart valve replacements